EP2918894A1 - Device and method for safety shut-off of liquefied gas installations - Google Patents

Abstract

The present invention relates to a method for detecting leaks in a conduit system for transporting fluids, comprising a feed line (40) and at least one venting outlet (75) and a supply outlet (80), wherein in the feed line (40) first valve (60) with a pilot leak (62), in the vent-discharge line (75) to the environment a second valve (70), with a series-arranged limiter (72), and in the region of the first valve (60) a measuring device (67) for determining a pressure difference, is arranged. The method comprises the following steps: (a) determining the differential pressure of the fluid with the measuring device (67) between a first pressure (P1) in the supply line (40) and a second pressure (P2) in the supply discharge line (80 ), or in the vent-discharge (75) before the second valve (70); (b) calculating a maximum volume flow of the pilot leak (62) as a leak rate of the first valve (60); (c) continuously determining the differential pressure between the first pressure (P1) in the supply line (40) and the second pressure (P2) in the supply discharge line (80) and calculating the actual volume flow. The method is characterized in that an actual volumetric flow whose value is approximately equal to the maximum volumetric flow rate after step (b) indicates an unacceptable leak (85) in the supply discharge line (80), and an actual volumetric flow whose value is smaller is less than or equal to 100% and greater than 0% of the maximum volumetric flow, indicating substantially no leakage (85) in the supply drain (80).

Description

The present invention relates to a device and a method for safety shut-off of LPG systems for preventing unwanted release of gas, especially on vehicles, for example on boats. Leaking pipe systems of liquefied gas installations or defective gas appliances represent a considerable hazard potential. Espe- cially aboard ships, escaping propane or butane gases collect at the lowest point of a hull. Thus even small amounts of leakage inside the hull can lead to ignitable gas concentrations.

Safety shut-offs of liquefied gas installations are known in the art. For example, DVGW Code of Practice G 608, Section 5.4, describes a leak test method in which the piping systems are initially pressurized with air at a pressure of 150 mbar. After a waiting time of 5 minutes to set the thermal equilibrium, the pressure is read, for a further 5 min, the measured pressure may be max. fall by 5 mbar. The leak rate q _L (in cm ³ / h), according to DIN EN 13611: 2011-12 Annex D, is calculated from the pressure drop using the following equation: $${\mathrm{q}}_{\mathrm{L}}=\mathrm{11}.\mathrm{85}\cdot {\mathrm{10}}^{-\mathrm{3}}\cdot \mathrm{total\; volume}\left({\mathrm{P}}_{\mathrm{measurement\; start}}-{\mathrm{P}}_{\mathrm{measuring}}\right)$$

However, this leakage test test is not practical during normal operation of the liquefied gas system, because on the one hand, a pressure must be generated, which is above the system pressure and therefore requires additional effort, and on the other must prevail during the measurement, a thermal equilibrium in the lines.

Further, in the prior art, there are leakage test testing solutions which visualize gas bubbles as leaks form in the conduits. However, these sight glasses must be mounted at the feed point of the gas system due to their physical mode of action (flow switch). So you are usually out of sight of the user when operating the gas system. These so-called leakage testers can not be used in regular operation. The user must switch to "test mode" at the test device and then observe the possible blistering in the sight glass. These devices do not automatically monitor the tightness of the gas system and the connected modules.

Also known in the art are so-called gas remote switches which allow the user to disconnect the gas supply from the consumers through an electrical valve on the gas cylinder. Here, however, no monitoring function is included. The safety gain is based on keeping the system pressure-free when not in use. A leak-free test function is not available with these devices.

Also known in the art are hose rupture stops. These trigger when a sudden and complete tearing of the line, i. if the gas consumption of the system exceeds a specified maximum value. This is usually set at small installations to about 1.5 kg LPG per hour. In case of gradual damage or small leaks a hose rupture protection does not trigger; a gas outlet is thus not prevented. However, especially in poorly ventilated environments, for example in boats, gas accumulation may occur even in the case of small leaks, reaching a critical size.

In addition, leak gas safety valves are known in the prior art. However, they require an installation with double-walled cables. Such an installation is complex and not given in commercial systems. In the event of a leak in the outer jacket of the pipe, leakage gas relief valves detect the pressure loss between the inner and outer jacket and automatically interrupt the gas supply. A leak that occurs on non-double-walled system components, for example on the consumer or on the valves, is not recognized.

Starting from this prior art, it is an object of the present invention, at least partially overcome or to improve the disadvantages of the prior art.

The above object is achieved by a method according to the invention for detecting leaks in a conduit system for transporting fluids according to claim 1 and by a device according to claim 10. Particularly preferred embodiments are the subject of the dependent claims.

1. (a) Der Differenzdruck des Fluids wird mit dem Messgerät zwischen einem ersten Druck (P1) in der Zuleitung und einem zweiten Druck (P2) in derVersorgungs-Ableitung, bzw. in der Entlüftungs-Ableitung vor dem zweiten Ventil bestimmt.
2. (b) Anschließend wird ein maximaler Volumenstroms des Pilotlecks, als Leckrate des ersten Ventils, berechnet.
3. (c) Dann wird kontinuierlich der Differenzdruck zwischen dem ersten Druck (P1) in der Zuleitung und dem zweiten Druck (P2) in derVersorgungs-Ableitung bestimmt und daraus dertatsächliche Volumenstrom berechnet.

The inventive method for detecting leaks in a conduit system for the transport of fluids, in particular gas from liquefied gas installations, has a supply line, at least one venting outlet and a supply outlet. In this case, in the supply line, a first valve with a pilot leak, in the vent-discharge to the environment a second valve, arranged with a series limiter, and in the region of the first valve, a measuring device for determining a pressure difference. The method, using the indicated structure, comprises the following steps:

1. (a) The differential pressure of the fluid is determined by the meter between a first pressure (P1) in the supply line and a second pressure (P2) in the supply line and in the bleed line before the second valve.
2. (b) Subsequently, a maximum volume flow of the pilot leak, as the leakage rate of the first valve, calculated.
3. (c) Then, the differential pressure between the first pressure (P1) in the supply line and the second pressure (P2) in the supply derivative is continuously determined, and from this, the actual volume flow is calculated.

According to the invention, an actual volumetric flow whose value is approximately equal to the maximum volumetric flow rate after step (b) then indicates an unacceptable leak in the supply outflow. Furthermore, an actual volumetric flow whose value is less than 100% and greater than 0% of the maximum volumetric flow rate after step (b) indicates substantially no leakage in the supply drainage.

A plant according to the invention for transporting fluids, in particular a liquefied gas plant, has a tank. This usually consists of one or more gas cylinders containing propane gas, butane gas or another liquefied gas and which are under pressure, for example between 2 to 8 bar overpressure. This fluid, in particular the LPG, is via a shut-off valve and a pressure reducer connected to a piping system. The pressure reducer reduces the high gas pressure from the tank to a first pressure P1 of 30 mbar, or to 50 mbar for old systems, which is applied to the piping system. The piping system leads to a consumer, eg to a stove or a heater. In front of the consumer, a shut-off valve (AV) is arranged, with which the gas supply to the consumer can be switched on and off as needed. The duct system has a certain volume and, depending on the type of vehicle in which it is installed, may have a length of about 2 m to 10 m.

The conduit system may have one or more leaks. A leak in the sense of this invention can be caused for example by a loose hose clamp or damage in the pipe system, such as a sharp object. But such a leak can also be a big leak, e.g. caused by tearing off a hose. Such leaks, which lead to an actual volume flow of the pilot leak, the value of which corresponds approximately to the maximum volume flow after step (b), are regarded as a non-permissible leak. However, very small leaks, especially when taken together in the entire piping system, have a volumetric flow that is less than 100% and greater than 0% of the maximum volumetric flow rate after step (b) are considered to be a permissible leak or not a leak.

Between the pressure reducer and the line system, a valve and sensor unit (VSE) is connected in the inventive method, with which the monitoring of the liquefied gas system is carried out for leaks. The VSE thus has a supply line which is connected to the coming from the tank pressure reducer; this is under a first pressure P1. Further, the VSE has a utility drain leading to the piping - and finally to the consumer. The supply drain and the pipe system have a pressure P2. Between the supply line and the supply line, a first valve, the release valve FV, is arranged in the VSE. Parallel to this first valve is a limiter called pilot leakage. Further, parallel to the first valve, there is a meter, preferably a differential pressure meter, which measures the differential pressure between the pressure P1 from the pressure reducer and the pressure P2 of the supply drain and the piping.

Furthermore, the VSE has a venting outlet that leads to the environment. The environment has an ambient pressure P0. Between the venting outlet and the supply outlet, a second valve, the venting valve EV, is arranged in the VSE. In series with the second valve, a limiter is arranged.

In a step (a) of the method according to the invention, the differential pressure P _{diff of} the fluid between the first pressure P1 in the supply line and the second pressure P2 in the supply discharge line is determined. In an arrangement according to the invention, the pressure P2 is also present in front of the second valve, which leads to the venting discharge. The differential _pressure P _diff can assume two extremes: when the first valve (FV) is open and the second valve (EV) and the shut-off valve (AV) are closed, then (in the steady state, ie after the effects of the gas have subsided -Input) P2 = P1, and the differential pressure is P _diff ≈ 0. The other extreme is when the first valve (FV) is closed and the second valve (EV) is open; This happens during the so-called venting of the pipe system. Here, P2 = P0, and the differential pressure is thus P _diff = P1 - P0. This is the maximum differential _pressure P _{diff max} at the differential pressure gauge. These measurements can also be used to verify the functionality of the two valves (FV, EV) and the meter. For a functional check of the overall system - and in particular the measuring devices - the piping system can also be partially vented during normal operation; then a change of the differential _pressure P _diff must be determined.

In a step (b), the maximum volume flow of the pilot leak is calculated. For this purpose, first the line system is vented. Then, when the second valve (EV) is closed, the gas flows into the piping system only via the pilot leak; the pressure P2 rises slowly until it reaches P1. Thus, the maximum volume flow c1 of the pilot leak, at the beginning of the pressure rise after venting, when P2 = P0, can be calculated as follows: $$\mathrm{c}\mathrm{1}=\mathrm{total\; volume}\cdot \frac{\mathrm{dP}\mathrm{2}}{\mathrm{dt}}\cdot \frac{\mathrm{1}}{\left(\mathrm{P}\mathrm{1}-\mathrm{P}\mathrm{2}\right)}$$

During normal operation of the LPG system, in a step (c), the differential pressure P _diff between the first pressure P 1 in the supply line and the second pressure P 2 in the supply discharge or in the venting discharge upstream of the second valve can be determined continuously and from this the actual volume flow can be calculated. If the first (FV) and the second valve (EV) are closed, and when an actual volumetric flow is measured, the value of which corresponds approximately to the value of the maximum volumetric flow c1 of the pilot leak, then it can be inferred according to the inventive method, that in the supply derivative or in the connected thereto piping system a no longer permissible leak is located. If a very small actual volume flow is measured in a method according to the invention, in particular a volume flow whose value is less than 100% and greater than 0% of the maximum volume flow after step (b), then there is an indication of essentially no leak - ie a very small one or no leak - in the supply line or in the line system connected to it. Based on this information, measures for alarming as well as direct controlling interventions can be made.

Therefore, this method results in the advantage according to the invention that leaks in a line system for transporting fluids, in particular gas in liquefied gas installations, can be continuously monitored. This can be done without special test sequences, without further measures on the line system - such as. a double-walled pipe - and without having to consider thermal boundary conditions. Furthermore, said method is so robust that it can also be used with high reliability in mobile environments, e.g. in land vehicles or boats.

One embodiment of the method according to the invention for detecting leaks in a line system is that an actual volume flow whose value corresponds to between 100% and 10% of the maximum volume flow after step (b) indicates a leak in the supply line.

Thus, not only a large leak or no leak is distinguishable with the method according to the invention, but it can be in metrologically determined limits, each leak rate as a threshold value for a permissible leak specify. If the first (FV) and the second valve (EV) and the shut-off valve (AV) are closed and there is no leak in the supply line or in the line system, then in a steady state the value of the differential _pressure P _diff depends only on Ratio of the maximum flow rate c1 of the pilot leak to the maximum flow rate c2 of the limiter, which is arranged parallel to the second valve. It is assumed that the limiter, which is arranged in series with the second valve, a has significantly higher maximum flow than c2. This results in the differential _pressure P _diff , in the stationary state and without a leak in the supply derivative, too $${\mathrm{P}}_{\mathrm{diff}}=\mathrm{P}\mathrm{1}-\mathrm{P}\mathrm{2}\approx \left(\mathrm{P}\mathrm{1}-\mathrm{P}\mathrm{0}\right)\cdot \frac{\mathrm{c}\mathrm{2}}{\mathrm{c}\mathrm{1}+\mathrm{c}\mathrm{2}}$$

When a leak occurs in the supply drain, a higher differential pressure P _diff sets in. Assuming, for example, that c2> c1, ie that a leak has occurred in the supply lead, then a differential pressure P _diff > (P1-P0) * 1/2 results. This difference to a differential pressure without a leak can be detected with high robustness. Since the volume flow c1 of the pilot leak and c2 of the limiter of the second valve are known, a threshold value can be selected within wide limits, from which point a leak is regarded as no longer permissible. As a rule, a differential _pressure P _diff > 0.5 · P _{diff max is} assumed to be the highest threshold value. The choice of the lowest threshold depends on the one hand on specifics of the specific system and possibly on customer wishes, on the other hand it depends on the measuring range of the differential pressure measuring device. In the case of commercially available differential pressure measuring devices, a differential _pressure P _diff > 0.1 · P _{diff max can} still be reliably detected. It follows that an actual volumetric flow whose value is between less than 100% and greater than 5%, preferably between less than 100% and greater than 10%, of the maximum volumetric flow rate after step (b), indicates a leak in the size of the pilot leak in the supply line. Derivative points and thus can be set in this area as a threshold for a permissible leak. On this basis, measures for alerting, etc. can then be made. It will be appreciated that the present invention can be used for a variety of conduit systems through the wide range that results in choosing the allowable leak threshold to allow for continuous control of these conduit systems for leaks. A further broadening of the measuring range by selecting a more sensitive differential pressure measuring device is possible and within the meaning of this invention.

A further embodiment of the method according to the invention, with at least the venting outflow and the second valve (EV), between the supply outflow and the environment, determines - before determining the differential pressure according to step (a) - a total volume of the supply derivative, by Pressure in the supply drain is lowered by opening the second valve substantially to the pressure of the environment, and by the volume flow through the second valve and a delimiter during venting over the period until about the pressure of the environment is reached, integrated, in particular numerically summed, is.

Since the volume flow of the pilot leak is known, by integrating the volumes that flow through the pilot leak, the total volume of the supply derivative, or the line system connected thereto, can be determined according to the following equation $$\mathrm{total\; volume}=\int \frac{\mathrm{c}\mathrm{1}}{\mathrm{11}.\mathrm{85}\cdot {\mathrm{10}}^{-\mathrm{3}}\cdot \left(\mathrm{P}\mathrm{1}-\mathrm{P}\mathrm{2}\right)}\mathrm{dt}$$

Thus, after venting, the differential pressure P _diff = P1 - P2 is observed and integrated over the observation time until approximately the pressure of the environment is reached. Because the observation intervals in a real technical system can not be arbitrarily short, in the technical solution the differential pressure after each observation interval, preferably once per second, is determined and numerically summed. Since the sensor also has a limited sensitivity for the differential pressure, it has proven expedient to terminate the numerical summation when a value of 0.5 × (P1-P0) has been reached, and to estimate the total volume of the line system on this basis.

In one embodiment of the method according to the invention, to determine the actual volume flow of the fluid, the first valve (FV), between the supply line and the supply outlet, is closed, and a pilot leak, between the supply line and the line system, is opened.

In this embodiment, the maximum flow rate c1 and also the maximum differential pressure P _diff = P1-P0 are known. Since the volumetric flow of the fluid is proportional to the differential pressure, the actual volumetric flow can be determined from the differential pressure continuously detected with said measuring device, on the condition that during the measurement the first valve (FV) is closed and a pilot leak is opened. This has the advantage that the pilot leak, together with the meter, can be easily used for continuous monitoring of the piping system for a leak. This results in a significant advantage over all the prior art methods because these methods do not allow continuous measurement and / or require special intervention in the piping system for a measurement.

In one embodiment of the method according to the invention, the maximum volume flow of the pilot leak after venting and the closing of the second valve from the pressure rise after, in particular immediately after, the closing of the second valve is determined.

If the maximum volume flow c1 of the pilot leak is not known or should be determined anew, eg to check the function of the overall system, then the state in which the maximum differential pressure P _{diff max} is present at the ends of the pilot leak is suitable. This is, according to the above considerations, P _{diff max} = P1 - P0. This condition is reached after venting, especially at the moment when the second valve (EV) is closed. During venting and also during this measurement, the first valve (FV) is closed.

In one embodiment of the method according to the invention, the maximum volume flow of the pilot leak is calculated from the flow resistance of the pilot leak, wherein the maximum volume flow preferably has a value between 2 cm ³ / h and 50 cm ³ / h.

If the first and the second valve are closed and no or a very small leak in the supply derivative is assumed, then results as a steady state that the differential pressure measuring instrument, which is parallel to the first valve, a pressure P _diff = (P1 - P2) gives; on the series circuit of the leakage-vent valve with the flow restrictor of the vent line results in a pressure P2 - P0. If now the volume flow of the volume flow restrictor of the vent line is assumed to be substantially greater than the volume flow of the leakage vent valve and the latter as equal to the volume flow of the pilot leak, then results in said steady state, a pressure at the differential pressure measuring device of P _diff = ( P1 - P2) ≈ 0.5 · (P1 - P0). This means that this measurement d. H. when the first and second valves are closed - a simple and continuous check is whether the component parameters have changed significantly. It can thus be determined with this measurement and compared to the values of the initial startup, which were determined with the inventive steps (a) and (b), for example, if one of the limiters is clogged, ie if the maximum volume flow of the limiter changed has, or of course, whether a leak in the supply derivation emerged is. It should be emphasized that these values are to be understood only as an example, for better understanding.

In one embodiment of the method according to the invention, a control unit detects or determines the actual volume flow and closes the first valve (FV), in particular if the volume flow through the leak is greater than or equal to the volume flow through the pilot leak.

A control unit which operates according to a method according to the invention can thus detect a leak, in particular an impermissible leak. It is particularly advantageous that this monitoring of the line system is carried out continuously. An impermissible leak is considered to be such a leak in the supply outlet or in the line system, which has a volume flow that is greater than or equal to the volume flow through the pilot leak. Once an improper leak has been detected, the controller closes the first valve (FV) to inhibit further gas delivery into the piping system. It is within the meaning of the present invention, when the closing of the first valve with a clear message, for example, with an acoustic and / or optical and / or mechanical alarm, is connected. This message may also be relayed over a wired or wireless communication channel, for example to on-board electronics or to centralized monitoring.

It is convenient to perform the determination of the differential pressure between the pressure P1 in the supply line and the pressure P2 in the supply drain and to calculate the actual volume flow at regular time intervals. A compromise between a fast response time and the load of a battery is desirable. In practice, a time interval of preferably 0.5 to 5 seconds, more preferably of one second, between two measurements has been found to be particularly suitable.

In another embodiment of the method according to the invention, the determination of the differential pressure between the pressure P1 in the supply line and the pressure P2 in the supply discharge and the calculation of the actual volume flow is also carried out when the shut-off valve is open.

The shut-off valve (AV) is always open when the consumer is switched on. In this situation, the first valve FV is also open. But this results in a significantly different Differential _pressure P _diff = P1 - P2. The pressure drop then does not take place at the - quite small - pilot leak, but at the first valve whose maximum volumetric flow is significantly greater than that of the pilot leak. Nevertheless, it is very useful to monitor the differential pressure in this mode of operation as well: On the one hand, a hose break can be reliably detected because the maximum volume flow of the shut-off valve to the consumer is significantly lower than a volume flow that occurs in the event of a hose break. On the other hand, the measured values can also be evaluated for consumption measurement.

In one embodiment of the method according to the invention, an overpressure, preferably an overpressure of less than 0.15 bar, more preferably between 30 and 50 mbar, in each case based on the pressure P0 of the environment, is applied to the feed line of the fluid.

According to DVGW Code of Practice G 608, the operating pressure (nominal value) for LPG in recreational vehicles is 30 mbar; for old systems, i. for liquefied gas installations that have been installed in accordance with DVGW Code of Practice G 608: 1985-02 and earlier, 50 mbar. For catering facilities, the operating pressure is 150 mbar. Devices embodied according to one embodiment of the method according to the invention are therefore preferably designed for these two fields of use.

1. (a) Bestimmen des Differenzdrucks des Fluids mit dem Messgerät zwischen einem ersten Druck in der Zuleitung und einem zweiten Druck in derVersorgungs-Ableitung, bzw. in der Entlüftungs-Ableitung vor dem zweiten Ventil.
2. (b) Berechnen eines maximalen Volumenstroms des Pilotlecks, als Leckrate des ersten Ventils.
3. (c) Kontinuierliches Bestimmen des Differenzdrucks zwischen dem ersten Druck (P1) in der Zuleitung und dem zweiten Druck (P2) in der Versorgungs-Ableitung und berechnen des tatsächlichen Volumenstroms, dadurch gekennzeichnet, dass ein tatsächlicher Volumenstrom, dessen Wert etwa dem maximalen Volumenstrom nach Schritt (b) entspricht, auf ein nicht mehr zulässiges Leck in derVersorgungs-Ableitung hinweist, und ein tatsächlicherVolumenstrom, dessen Wert kleiner als 4 cm³ / h ist, auf im Wesentlichen kein Leck in derVersorgungs-Ableitung hinweist.

The present invention also includes an apparatus for detecting leaks in a conduit system for transporting fluids having a supply line, at least one bleed line and a supply line and a controller. In this case, in the supply line, a first valve with a pilot leak, in the vent discharge to the environment a second valve, arranged in series with a limiter, and in the region of the first valve, a measuring device for determining a pressure difference, and the controller includes at least Inputs for the values from the meter and outputs for controlling the first valve and the second valve. The device is characterized in that a method is implemented in the control device, comprising the following steps:

1. (A) determining the differential pressure of the fluid with the meter between a first pressure in the supply line and a second pressure in the supply lead-out, or in the venting lead-off before the second valve.
2. (b) Calculating a maximum volume flow of the pilot leak, as the leakage rate of the first valve.
3. (c) continuously determining the differential pressure between the first pressure (P1) in the supply line and the second pressure (P2) in the supply discharge and calculating the actual volume flow, characterized in that an actual volume flow whose value is about the maximum volume flow after step (b) corresponds, indicating a no longer admissible leakage in derVersorgungs derivative, and a tatsächlicherVolumenstrom whose value is less than 4 cm ³ / h is substantially indicative of a leak in derVersorgungs lead.

The device according to the invention is preferably arranged between a pressure reducer, from a tank, and a supply outlet, which leads to a line system. Furthermore, the device has a venting derivation, for venting the piping system into the environment, with an ambient pressure P0. The device according to the invention is hereinafter referred to as valve and sensor unit (VSE). Between the supply line coming from the pressure reducer and the supply drain, a first valve, the release valve FV, is placed in the VSE. The pilot leak can be designed as a flow restrictor, in particular as a calibrated flow restrictor. Parallel to this first valve is a limiter called pilot leakage. Further, parallel to the first valve, there is a meter, preferably a differential pressure meter, which measures the differential pressure between the pressure P1 from the pressure reducer and the pressure P2 of the supply drain and the piping. Between the venting lead and the lead-off lead, a second valve, the bleed valve EV, is placed in the VSE. Parallel to the second valve, another limiter is arranged. Further, a limiter is arranged in series with the second valve.

In a preferred embodiment, the VSE is housed in a bottle crate. The VSE is preferably completely encapsulated and sealed gas-tight. A control module is usually installed elsewhere. In particular, the control module includes control logic to drive the valves, signal conditioning of the signals from the meter to monitor the VSE, and power to the VSE. For example, the control logic for boats is inside the hull.

In a step (a) of the method according to the invention, the differential pressure P _{diff of} the fluid between the first pressure P1 in the supply line and the second pressure P2 in the supply discharge line is determined. In an arrangement according to the invention, the pressure P2 is also present in front of the second valve, which leads to the venting discharge. The differential _pressure P _diff can assume two extremes: it is maximum when the line system is vented; where P _diff = P1 - P0. The differential pressure is minimal, P _diff ≈ 0, when the first valve (FV) is open and the second valve (EV) and the shut-off valve (AV) are closed. These extremes can also be used as reference points for measurements and to verify the functionality of the two valves (FV, EV) and the meter.

In step (b) the maximum volume flow of the pilot leak is calculated. For this purpose, a measurement is particularly suitable if the differential _pressure P _{diff is} maximum. This maximum volume flow of the pilot leak is referred to as the leakage rate of the first valve.

These steps (a) and (b) may be performed even if the pilot leak is a calibrated limiter. It can thus be checked whether the parameters of the system that are relevant for the measurement are still unchanged. In practice, steps (a) and (b) are performed only at initial startup or after the system has been changed. It is also possible to check these steps and to increase the measurement safety at any time intervals. In cases where no differential pressure is to be measured, the line can be partially vented for internal function control, in order to observe a subsequent pressure equalization can.

In step (c), the differential pressure P _diff = P1 - P2 between the first pressure P1 in the supply line and the second pressure P2 in the supply derivative is continuously determined. The measured values that are determined can be related to the maximum volume flow of the pilot leak - from step (b) - and from this the actual volume flow can be calculated.

On the basis of these measurements, the VSE can determine whether a leak has occurred in the supply discharge line or the line system arranged behind it: If the actual volume flow reaches a value that corresponds approximately to the maximum flow rate after step (b), then In the supply derivation a not more permissible leak arose. If the actual volume flow is very small, ie assumes a value less than 20%, preferably less than 10%, particularly preferably less than 5%, of the maximum volume flow after step (b), then this gives an indication of essentially no leakage. ie a very small or no leak - in the supply line or in the line system connected to it. Based on this information, the VSE can take both alarming and direct control actions.

It should be pointed out that not only a large leak or no leak can be distinguished with the method according to the invention, but it is possible to specify any leakage rate as a threshold value for a permissible leak in metrologically determined limits. If the first (FV) and the second valve (EV) and the shut-off valve (AV) are closed and there is no leak in the supply line or in the line system, then in a steady state the value of the differential _pressure P _diff depends only on Ratio of the maximum flow rate c1 of the pilot leak to the maximum flow rate c2 of the limiter, which is arranged parallel to the second valve. If c1 and c2 are approximately equal, then Eq. 3 is a differential _pressure P _diff ≈ (P1-P0) * 1/2. If the differential pressure is higher, then a leak has occurred. Since the volume flow c1 of the pilot leak and c2 of the limiter of the second valve are known, a threshold can be selected within wide limits, from which a leak is considered no longer permissible and measures for alarming, etc. are made. The upper threshold, however, is de facto determined by legislation by the legislator, in accordance with the DVGW Code of Practice G 608 mentioned above, which contains a threshold value for the leakage test. According to Eq. 1, this threshold is for example for a 2 meter long gas line with 6 mm inner diameter about 4 cm ³ / h.

Thus, a device according to the invention not only has the advantages of continuous monitoring according to the invention, neither additional design measures on the line system nor consideration of the thermal boundary conditions are required, but also has a robust measurement method, including effective test and control functions, and a very easy installability on.

In one embodiment of the device according to the invention, the first valve and / or the second valve can be opened or closed electromagnetically or pneumatically, in particular positively controlled closed.

The device described can preferably be used as a safety device for liquefied gas installations. This results in high demands on reliability and security against manipulation. For this purpose, the first valve and / or the second valve can be opened or closed electromagnetically or pneumatically; This makes it possible to automatically interrupt the gas supply in case of failure. Furthermore, it is ensured by the control circuits, in particular by electronic control circuits, that the monitored with this device LPG system can not be used by the user or an external person accidentally or intentionally despite a leak or malfunction. To further enhance tamper resistance, in a particularly preferred embodiment, the controller is packaged, sealed or, e.g. in an epoxy resin, poured.

In an embodiment of the device according to the invention, the power supply of the control device has a current limit, preferably a current limit against short-time exceeding of a maximum current, particularly preferably an irreversible current limit. This measure can further reduce the likelihood of a malfunction, incorrect operation or faulty installation or installation.

Said device is designed to be used in a stationary and / or mobile environment, preferably on a land vehicle, an aircraft or a watercraft.

The invention will be described with reference to various embodiments, wherein it should be noted that the invention is not limited to the embodiment shown here, but rather also corresponding modifications in the sense of the present invention.

• Fig.1: die schematische Darstellung eines erfindungsgemäßen Gesamtsystems;
• Fig. 2: die schematische Darstellung der erfindungsgemäßen Ventil- und Sensor-Einheit (VSE);
• Fig. 3: den Verlauf des relativen Differenzdrucks in Abhängigkeit vom Leck-Volumenstrom;
• Fig. 4: ein Beispiel einer erfindungsgemäßen Ventil- und Sensor-Einheit (VSE) in der Aufsicht;
• Fig. 5: ein Beispiel erfindungsgemäßen Ventil- und Sensor-Einheit (VSE) als Schnittdarsteltung.

Showing:

• Fig.1 : the schematic representation of a total system according to the invention;
• Fig. 2 : the schematic representation of the valve and sensor unit (VSE) according to the invention;
• Fig. 3 : the course of the relative differential pressure as a function of the leakage volume flow;
• Fig. 4 : an example of a valve and sensor unit (VSE) according to the invention in the plan view;
• Fig. 5 : An example according to the invention valve and sensor unit (VSE) as Schnittdarsteltung.

Fig.1 schematically shows a device according to the invention, in a typical environment, ie in a liquefied gas plant. In this case, the subsystems of the liquefied gas system are clearly recognizable: the fluid unit 10, the consumer unit 90 and, in between, the line system 80. The fluid unit 10 is preferably accommodated in a bottle crate. Within the fluid unit 10, a tank or a gas cylinder 30 is arranged, which serves to supply the system with the liquefied gas; Of course, this can also be a battery of several gas cylinders. To the gas cylinder 30, a shut-off valve 32 and a pressure reducer 35 is connected. The pressure reducer 35 reduces the high pressure of the gas cylinder 30 to a pressure P1 of 30 mbar for recreational vehicles or to 50 mbar for old systems. For catering systems, the operating pressure applied to the pressure reducer35 is 150 mbar. Via a feed line 40, the pressure reducer 35 is connected to the valve and sensor unit (VSE) 50. The VSE indicates a vent derivate, to the environment, 75. The environment has an ambient pressure P0. If necessary, the piping system 80 can be vented via the venting outlet. The line system 80 also represents the supply derivation 80 of the VSE 50. To better clarify the pressure and volume conditions, the volume 81 of the supply line or the line system 80 is depicted as a separate element. The conduit system 80 may be of considerable length depending on the type of vehicle in which it is installed, typically from less than 5 meters to over 20 meters. The conduit system 80 may also include one or more leaks or leaks 85 that may be due to accident, misuse or wear. The consumer unit 90 consists of the actual consumer 95 and a shut-off valve 92, via which the consumer 95 can be switched on and off. The LPG system is put into operation by opening the shut-off valve 32. When opening the shut-off valve 32 and the VSE 50 is turned on, which interrupts the supply of the conduit system 80 with gas in case of leaks or malfunction. The use of the gas in the consumer 95 is made possible by opening the shut-off valve 92.

Fig. 2 schematically shows the details of the VSE 50. Via the feed line 40, in which a pressure P1 prevails, the gas enters. This is followed by a first valve, the release valve (FV) 60, on. Parallel to the release valve 60, a calibrated limiter, the pilot leak 62, is arranged. Parallel to this is a measuring device 67 is arranged, which is designed as a differential pressure measuring device. A second valve, the vent valve (EV) 70, is used to vent the line system 80. Parallel to the vent valve 70, a limiter 72 is arranged, which represents a possible leak in the vent valve 70. In series with the vent valve, a further limiter, the flow restrictor of the vent line 74, is arranged. To vent the line system 80, the release valve 60 is closed and the vent valve 70 is opened. After venting prevails in the pipe system 80, the pressure P0 of the environment. The venting usually takes place when the vehicle is parked longer; however, it may also be performed to verify the correct functioning of the VSE or meter 67. The gas is withdrawn via the supply outlet 80, to the line system.

Based on Fig. 2 the operating modes of the VSE 50 are clarified: For venting the release valve 60 is closed and the vent valve 70 is opened. In normal operation, the release valve 60 is open and the vent valve 70 is closed. In lock mode, both valves 60, 70 are closed. The lockout mode occurs when the load 95 has been shut down or when an error has occurred. The lockout operation is also the preferred state during leak measurement.

Fig. 3 shows (on the y-axis) the curve of the relative differential pressure P _{diff rel} , based on the maximum differential pressure P _{diff max} , above the leakage volume flow q _{L rel} a leak 85 (on the x-axis), the volume flow of the pilot leak 62 is related. It can clearly be seen that in the case of a leak volume flow q _{L rel} = 1, ie if the overall system has a leak in the size of the pilot leak 62, a relative differential pressure P _{diff rel} = 0.5 * P _{max occurs} at the differential pressure gauge , This is also evident from the calculations above. Furthermore, it can be seen that, with a well detectable measuring range of 0.1 to 0.9 · P _max, a leakage volume flow q _{L rel} of 0.1 to 10 · q _{L rel} can be measured. Together with the legal requirement that a leak with a q _{L rel} > 1 is not permitted, can therefore with an inventive device with a differential pressure gauge, which has a measuring range of 0.1 to 0.9 · P _max , any Threshold of 0.1 to 1 · q _{L rel can be selected} for a maximum allowable leak.

Fig. 4 shows an example of a valve and sensor unit (VSE) 50 according to the invention, partially schematically in plan view. In this case, in the VSE main body 51, the connections for the supply line 40th and the supply lead 80 and the wiring within the VSE main body 51 can be recognized as dashed lines. Further, the positions 60a and 70a are shown, on which the release valve 60 and the vent valve 70 are arranged, in an external view. The differential pressure measuring device 67 is shown schematically at the edge of the VSE main body 51, one of which leads to the feed line 40 (on the release valve 60) and the other end of which leads to a feedthrough 80. As the differential pressure sensor in the differential pressure gauge 67, for example, the MPXV7007 type may be adopted by Freescale Semiconductor, which is implemented as a piezoresistive transducer.

In Fig. 5 is the section AB through the release valve 60 and the VSE main body 51 of Fig. 4 , shown, wherein the vent valve 70 is shown in a view from the outside. Again, the connections for the supply line 40 and the supply lead 80 and the wiring within the VSE main body 51 can be seen as dashed lines. The valve body 61 of the release valve 60 is shown in section. In this, a solenoid coil 64 is arranged. This acts on a valve piston 66, which is coupled to a return spring 65. When current flows through the solenoid 64, the valve piston 66 is drawn into the solenoid 64 and the valve 60 is opened in this way. In the embodiment of Figure 5 the pilot leak 62 is designed as a flow restrictor made of sintered metal. In this case, a bypass hole is drilled in the sealing washer 63. The vent valve 70 is constructed similar or the same as the release valve 60. It is shown here in the closed state, ie the sealing disc 73 is closed. The sealing disc 73 closes the vent hole 75 with the integrated flow restrictor 74, which is preferably designed as a 0.3 mm bore.

List of reference numbers

10

Fluid unit

30

Tank or gas bottle

32

Shut-off valve

35

pressure reducer

40

supply

50

Valve and Sensor Unit (VSE)

51

VSE base body

60

first valve / release valve (FV)

60a

Seat of the first valve / release valve (FV)

61

Release valve FV, valve body

62

(calibrated) limiter (pilot leak)

63

Sealing washer with bypass hole

64

solenoid

65

return spring

66

plunger

67

Measuring device (differential pressure measuring device)

70

second valve bleed valve (EV)

70a

Seat of second valve / vent valve (EV)

72

Limiter / leak in the vent valve

73

Vent valve EV, sealing disc (closed)

74

(calibrated) limiter / volume flow limiter of the vent line

75

Venting discharge (environment)

80

Supply derivation (line system)

81

Volume of the supply derivation (line system)

85

Leak (in the pipe system)

90

Consumer unit

92

Shut-off valve (AV)

95

consumer

P0

Pressure P0 (environment

P1

Pressure P1 (supply)

P2

Pressure P2 (piping system)

Claims (13)

A method for detecting leaks in a conduit system for transporting fluids, comprising a supply line (40) and at least one venting discharge line (75) and a supply discharge line (80), wherein In the supply line (40) a first valve (60) with a pilot leak (62), • In the vent-discharge (75) to the environment a second valve (70), with a series-arranged limiter (72), and In the region of the first valve (60), a measuring device (67) for determining a pressure difference, is arranged, with the steps: a) Determining the differential pressure of the fluid with the measuring device (67) between a first pressure (P1) in the supply line (40) and a second pressure (P2) in the supply outlet (80), or in the venting discharge line (75 ) in front of the second valve (70); b) calculating a maximum volume flow of the pilot leak (62) as a leak rate of the first valve (60); c) continuously determining the differential pressure between the first pressure (P1) in the supply line (40) and the second pressure (P2) in the supply discharge line (80) and calculating the actual volume flow, characterized in that an actual volumetric flow, the value of which corresponds approximately to the maximum volumetric flow rate after step (b), indicates a non-permissible leak (85) in the supply discharge line (80), and an actual volumetric flow whose value is less than or equal to 100% and greater than 0% of the maximum volumetric flow rate after step (b), indicating substantially no leakage (85) in the supply drain (80). The method of claim 1, wherein
an actual volumetric flow whose value is between less than 100% and greater than 5%, preferably between less than 100% and greater than 10% of the maximum volumetric flow rate after step (b), indicates a leak (85) in the supply outlet (80). The method of claim 1 or 2, including at least the venting outlet (75) and the second valve (70), between the supply outlet (80) and the environment, wherein
before determining the differential pressure according to step (a)
the pressure (P2) in the supply lead (80) is lowered by opening the second valve (70) substantially to the pressure (P0) of the environment, and in particular a total volume of the supply lead (80) is determined by the volume flow by the second valve (70) and a limiter (72) during venting over the period until about the pressure (P0) of the environment is achieved, integrated, in particular numerically summed, is. The method of claim 1, 2 or 3, wherein
for determining the actual volumetric flow of the fluid, the first valve (60), between the supply line (40) and the supply discharge line (80), is closed, and a pilot leak (62), between the supply line (40) and the line system (80) , is open. Method according to one of the preceding claims, wherein
the maximum volume flow of the pilot leak (62) after venting, and from the pressure increase after, in particular immediately after, the closing of the second valve (70) is determined. Method according to one of the preceding claims, wherein
the maximum volume flow of the pilot leak (62) is calculated from the flow resistance of the pilot leak (62), the maximum volume flow preferably having a value between 2 cm ³ / h and 50 cm ³ / h. Method according to claim 1, 2 or 6, characterized in that
a control unit detects or determines the actual volume flow and, in particular, when the volume flow through the leak (85) is greater than or equal to the volume flow through the pilot leak (62), closes the first valve (60). Method according to one of the preceding claims, wherein
the differential pressure between the pressure (P1) in the supply line (40) and the pressure (P2) in the supply discharge line (80) is determined and the actual volume flow is calculated when the shut-off valve (92) is open. Method according to one of the preceding claims, wherein
at the supply line (40) of the fluid, an overpressure, preferably an overpressure of less than 0.15 bar, more preferably between 30 and 50 mbar, each based on the pressure (P0) of the environment, is applied. Device for detecting leaks in a conduit system for transporting fluids, comprising a supply line (40), at least one venting outlet (75) and a supply outlet (80) and a control unit, wherein in the supply line (40) a first valve (60) with a pilot leak (62), in the vent-discharge (75) to the environment a second valve (70), with a series-arranged limiter (72), and in the region of the first valve (60), a measuring device (67) for determining a pressure difference, is arranged, and
the controller includes at least inputs for the values from the meter (67) and outputs for controlling the first valve (60) and the second valve (70),
characterized in that
in the control device, a method according to any one of claims 1 to 9 is implemented. Apparatus according to claim 10, characterized in that
the first valve (60) and / or the second valve (70) can be opened electromagnetically or pneumatically or closed, in particular positively controlled closed, can be. Apparatus according to claim 10 or 11, characterized in that
the power supply of the control device has a current limit, preferably a current limit against short-term exceeding of a maximum current, particularly preferably an irreversible current limit. Use of a device according to claim 10, 11 or 12 in a stationary and / or mobile environment, preferably on a land vehicle, an aircraft or a watercraft.

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